The present invention relates to a fast method for determining a flexible pipe structure or a list of structure families meeting determined specifications, for constituents of the structure industrially available and organized in databases.
The present invention relates to flexible pipes referred to as unbonded pipes according to the API RP 17B (Second Edition, Jul. 1, 1998) standard or to the API Spec. 17J standard. These standards, mentioned here by way of reference, explicitly describe the constituents of such a flexible pipe structure. The constituents considered here are all the constituents which take part, directly or indirectly, in the mechanical resistance and the thermal insulation of the flexible pipe during the laying operation and/or while it is used. The following constituents are mentioned: the body, the pressure layer, the hoop, the armors, the sheaths. Insulating materials can also be taken into account.
It is well-known that the combination of all above referenced structural elements involves complex calculations, notably because of the mechanical interdependences of each element. It is therefore advantageous to have a fast tool allowing examination of all the combinations of elements forming a flexible pipe meeting the specifications. Various solutions can thus be compared and classified according to various objectives: the lightest structure, the least expensive, the easiest to transport, the quickest to manufacture, etc.
The present invention thus relates to a method for determining a flexible pipe meeting specifications and consisting of at least one of the following elements: a body, a sealed sheath, a pressure layer, a hoop, an armoring layer, an insulating material layer. The method includes:
a) recording the data of the specifications corresponding mainly to the conditions of use and to the laying and manufacturing conditions of a pipe,
b) making up databases concerning each one of the constituents of the pipe,
c) performing all the combinations consisting of at least one of the elements of the group: body, pressure layer, hoop and sheath, defined in the data bases so as to form partial structures at least in accordance with the geometry of the pipe imposed by the specifications,
d) eliminating the combinations which do not meet the external pressure resistance imposed by the specifications,
e) determining for each combination from step d) the thickness and the armoring angle of the armors, and
f) classifying the combinations according to a determined criterion.
In the method, the geometry imposed in step c) can be the inside diameter of the pipe.
After step c), it is possible to keep only the combinations whose weight per unit of length is in accordance with that imposed by the specifications.
Step e) can be carried out by taking account of a calculated insulant thickness.
Step e) can be carried out from all the types of armoring wires selected from the corresponding database.
The combinations can be classified according to at least one of the following criteria: the weight per unit of length, the cost, the outside diameter, the safety coefficient at operating pressure, the collapse pressure, the maximum setting depth, the suspended weight when laid.
The databases used in step c) can be restricted to specific types of elements so as to limit the number of combinations.